Pitfalls in arterial enhancement timing

Imaging description Early arterial phase imaging is critical for high-quality CT angiography examinations; however, accurate imaging can be problematic in patients with large aneurysms or aortic dissections. In some cases, an early arterial acquisition may not allow enough time for complete filling of the aneurysm sac or false lumen with contrast (Figures 54.1–54.3). The incompletely opacified aneurysm sac or false lumen may appear thrombosed, when in actuality it is merely filled with unopacified blood. Swirling of contrast within the aneurysm sac is often present and can be a clue that incomplete contrast filling has occurred (Figure 54.3).Importance In the patient with acute pain, large aneurysms must be evaluated for signs of instability or rupture. One of the most critical findings is contrast extravasation reflective of active hemorrhage, which requires immediate repair. The case shown here (Figure 54.1) demonstrates how this important finding could be missed if the arterial timing did not allow for complete aneurysm filling. Patients with aortic dissection may have very slow flow in the false lumen, resulting in the appearance of pseudothrombosis of both the false lumen and the branches that arise from this lumen. As shown by the second case (Figure 54.2), a longer imaging delay will elucidate that the false lumen, arterial branch and end organ are actually perfused. The distinction is important because in the setting of arterial thrombosis intervention is necessary, whereas uncomplicated type B dissections do not require endovascular or surgical repair. Although much less common, proper characterization of a coronary artery aneurysm (Figure 54.3) as patent or thrombosed is critical to determine whether repair is indicated to avert rupture.Typicalclinical scenario Aortic aneurysms and dissections are two of the most common forms of aortic pathology. Patients may present acutely with pain, or may undergo serial imaging to guide management of previously diagnosed aneurysm or partially repaired dissection. Coronary aneurysms are much less common, particularly larger aneurysms. In adults, atherosclerosis is the most common cause, whereas in children it is Kawasaki disease.